The present invention relates generally to communications, and more specifically to improvements in Integrated Circuits for use in Radio Frequency/Microwave applications.
Many communication systems modulate electromagnetic signals from baseband to higher frequencies for transmission, and subsequently demodulate those high frequencies back to their original frequency band when they reach the receiver. The original (or baseband) signal, may be, for example: data, voice or video. These baseband signals may be produced by transducers such as microphones or video cameras, be computer generated, or transferred from an electronic storage device. In general, the high frequencies provide longer range and higher capacity channels than baseband signals, and because high frequency RF signals can effectively propagate through the air, they can be used for wireless transmissions as well as hard wired or fibre channels.
All of these signals are generally referred to as radio frequency (RF) signals, which are electromagnetic signals; that is, waveforms with electrical and magnetic properties within the electromagnetic spectrum normally associated with radio wave propagation. The electromagnetic spectrum was traditionally divided into 26 alphabetically designated bands, however, the International Telecommunication Union (ITU) formally recognizes 12 bands, from 30 Hz to 3000 GHz.
Wired communication systems which employ such modulation and demodulation techniques include computer communication systems such as local area networks (LANs), point-to-point communications, and wide area networks (WANs) such as the Internet. These networks generally communicate data signals over electrically conductive or optical fibre channels. Wireless communication systems which may employ modulation and demodulation include those for public broadcasting such as AM and FM radio, and UHF and VHF television. Private communication systems may include cellular telephone networks, personal paging devices, HF (high frequency) radio systems used by taxi services, microwave backbone networks, interconnected appliances under the Bluetooth standard, and satellite communications. Other wired and wireless systems which use RF modulation and demodulation would be known to those skilled in the art.
One of the current problems in the art is to develop filtering devices with the following characteristics:
physically small;
low power consumption;
inexpensive; and
have good performance characteristics.
For cellular telephones, and similar consumer items, it is desirable to have transmitters and receivers (which may be referred to in combination as a transceiver) which can be fully integrated onto inexpensive, low power, integrated circuits (ICs).
The continuing desire to implement low-cost, power efficient receivers and transmitters has led to intensive research into the use of highly integrated designs, an increasingly important aspect for portable systems, including cellular telephone handsets. This has proven especially challenging as the frequencies of interest in the wireless telecommunications industry (especially low-power cellular/micro-cellular voice/data personal communications systems) have risen above those used previously (around 900 MHz) into the spectrum above 1 GHz.
Attempts at completely integrated transceiver designs in Radio Frequency Integrated Circuits (RF IC)—also known as monolithic microwave integrated circuits (MMIC)—have met with limited success. Most such transceiver topologies require at least two high quality filters that hitherto have not been economically integrated within any modern IC technology.